Cohesion transpiration pull theory of ascent of sap was proposed by

A) Munch

B) Stephen Hales

C) Dixon and Joly

D) Bose

Transpiration is considered both necessary and harmful for plants. It is harmful because excessive water loss reduces soil water levels and may even cause plant death. However, it is necessary since it aids in water and mineral absorption, the ascent of sap, and also helps in cooling the plant by lowering leaf temperature.

• Why evil? It causes water loss.
• Why necessary? It drives the upward movement of water from roots to other plant parts. Despite lacking a heart or circulatory system, plants can move water upward through vascular tissues at rates up to 15 metres per hour.

Explained:

A) Munch – Proposed the Mass Flow (Pressure Flow) Hypothesis for food translocation via phloem.

B) Stephen Hales – Known as the Father of Plant Physiology; designed a ventilating machine.

C) Dixon and Joly – Proposed the Cohesion-Tension Transpiration Pull Model, explaining upward water transport due to transpiration pull from leaves. Only a small fraction of this water is used in photosynthesis and growth, while most is lost through stomata as transpiration.

D) J.C. Bose – Studied plant physiology and plant responses to stimuli.

Correct Answer: (C) Dixon and Joly